1. Field of the Invention
This invention relates to a roller bearing, and more particularly to a self-aligning roller bearing in which the side surfaces of the cross bars of a retainer are in surface contact with spherical rollers and the contact surface pressure of the retainer and the spherical rollers is low.
2. Description of the Prior Art
In a typical self-aligning roller bearing according to the prior art, as shown in FIGS. 1 to 3 of the accompanying drawings, a pair of metallic retainers 3 are disposed between an outer race 1 and an inner race 2. Each of these retainers 3 is such that an annular portion 4 inside the bearing and an annular portion 5 outside the bearing are connected together and made integral with each other by cross bars 6. A spherical section roller 12 is disposed in the pocket 11 of each retainer 3. The side surfaces 13 of the cross bars forming the pocket 11 have concavely curved surfaces 18 with axial and radical arcs of a curvature corresponding to the spherical rolling surface 17 of the roller 12, at the side of the bearing that is inward of a plane 16 perpendicular to a plane 15 containing the axis of the bearing and the axis 14 of the spherical roller, and containing the axis 14 of the spherical roller. The side surfaces 13 of the cross bars have a semicylindrical surface 19 outwardly of the plane 16.
Accordingly, the cylindrical surface 19 does not make surface contact but does make line contact with the spherical roller 12. Therefore, the area of contact between the side surfaces 13 of the cross bars and the spherical roller 12 is small and the contact surface pressure of the side surface 13 of the cross bar and the spherical roller 12 is high and thus, abrasion of the cross bars 6 is great. When the retainers 3 come into contact with the inner race 2 due to gravity, that is, when the retainers 3 shown in FIG. 3 move downwardly relative to the roller 12, the circumferential clearance between the roller 12 and the side surfaces 13 of the cross bars is great and the roller 12 becomes liable to be inclined and skewed. Also, since the spacing A between the outer peripheral surface 21 of a cross bar and the outer peripheral surface 21 of the adjacent cross bar is greater than the diameter of the corresponding portion of the spherical roller 12, the circumferential width dimension of the outer peripheral surfaces 21 of the cross bars is short and the rigidity of the cross bars 6 is weak. Further, the spherical roller 12 disposed in the pocket 11 falls off from within the pocket 11 through the cylindrical surface 19 during the assembly of the bearing and therefore, assembly of the bearing is difficult and also automation of the assembly of the bearing is difficult.